In a process of manufacturing a semiconductor substrate (hereinafter, referred to simply as a “substrate”), conventionally, various processings are performed by supplying a processing liquid onto a substrate. For example, performed is a cleaning process for washing out extraneous matters deposited on a surface of the substrate by supplying a cleaning solution onto the substrate.
In a substrate cleaning method disclosed in Japanese Patent Application Laid-Open No. 2010-56534 (Document 1), after a substrate having a surface on which a pattern is formed is heated to 140 to 300° C., droplets of a cleaning solution are supplied onto the surface of the substrate. Since the Leidenfrost phenomenon in which a vapor of the cleaning solution is interposed between the droplets of the cleaning solution and the substrate occurs on the substrate, the droplets of the cleaning solution do not enter between the patterns, being floating slightly above the substrate. Then, by the vapor sprayed from a lower surface side of the droplets of the cleaning solution onto the surface of the substrate, deposits such as residues or the like on the substrate are raised upward and removed. In the substrate cleaning method, since the cleaning solution does not enter between the patterns, it is possible to perform cleaning of the substrate while suppressing collapse of the patterns on the surface of the substrate.
On the other hand, in a substrate processing apparatus disclosed in Japanese Patent Application Laid-Open No. 2011-121009 (Document 2), a liquid film of a HFE liquid is formed on a surface of a substrate, and a liquid film of deionized water (DIW) on the liquid film of the HFE liquid. Then, by applying ultrasonic vibration to the liquid film of deionized water, a shock wave is applied onto the surface of the substrate and the surface of the substrate is thereby cleaned. In the substrate processing apparatus, since part of the shock wave caused by the ultrasonic vibration is reflected on an interface between the two kinds of liquid films, the energy of the shock wave to be applied onto the surface of the substrate decreases and the damage to the substrate is reduced.
Further, in a substrate processing apparatus disclosed in Japanese Patent Application Laid-Open No. 2010-238918 (Document 3), a processing of a substrate is performed by immersing the substrate with its main surface facing the side into a processing liquid pooled in a processing bath. When the processing is finished and the substrate is taken out upward from the processing liquid, part of the substrate which is positioned below a liquid surface of the processing liquid is heated to a temperature not lower than the boiling point of the processing liquid. Since the processing liquid between fine patterns on the main surface of the substrate is thereby vaporized, the surface tension of the processing liquid acting on the fine patterns decreases when the substrate passes through the liquid surface of the processing liquid, and it is possible to prevent the collapse of the fine patterns due to the surface tension.
In the substrate cleaning method disclosed in Document 1, there is a possibility that the deposits raised by the vapor from the droplets of the processing liquid may be diffused upward from the surroundings of the droplets and may fall onto the surface of the substrate to be deposited thereon again.